Automatic tension release for blind stitch sewing machines



Fig. 1.

Dec. 22, 1936. I BOWMAN 2,064,881

AUTOMATIC TENSION RELEASE FOR BLIND STITCH SEWING MACHINES Original Fi led Sept. 27, 1935 3 Sheets-Sheet l AAA Dec. 22, 1936. BOWMAN 2,064,881

AUTOMATIC TENSION RELEASE FOR BLIND STITCH SEWING MACHINES Original Filed se t. 27, 1935 3 Sheets-Sheet 2 I I I I g Dec. 22, 1936. G. BOWMAN AUTOMATIC TENSION RELEASE FOR BLIND STITCH SEWING MACHINES Original Filed Sept. 27, 1955 3 Sheets-Sheet 3 Laws 6. 50w/1AN Patented Dec. 22, 1936 UNITED sraras PATENT FFiE AUTOMATIC TENSION RELEASE FOR BLIND STITCH SEWING MACHINES Louis G. Bowman, St. Louis, Mo., assignor to Lewis Invisible Stitch Machine Company, St. Louis, Mo., a corporation of Maine 7 Claims.

This invention relates to new and useful improvements in sewing machines generally, although more particularly to improvements in means for releasing the needle thread tension employed in sewing machines of the blind stitch type.

This application constitutes a division of my copending application Serial No. 42,547, filed Sept. 27, 1935, for Improvements in sewing machines.

The principal object of the invention is to provide a tension release for the needle thread which is automatically operable upon depression of the pivoted work support whereby the stitched fabric may be readily withdrawn from the machine.

With the above and other objects in view which will more fully appear, the nature of the invention will be more clearly understood by following the description, the appended claims, and the several views illustrated in the accompanying drawings:

In the drawings:

Figure 1 is a front elevation of a blind stitch sewing machine embodying my invention,

Figure 2 is a top plan View thereof,

Figure 3 is a detail vertical section showing the means for pivotally mounting the work support, and

Figure 4 is a somewhat diagrammatic sectional view illustrating the automatic releasing of the needle thread tension by depression of the work support.

Like reference numerals designate corresponding parts throughout the several figures of the drawings.

My invention is shown as applied to a. blind stitch sewing machine which embodies a main frame including a base 5, a standard 6 having an arm I extending laterally from the upper end thereof, and a forwardly extending stitching head 8 secured to the free end of said arm. A horizontal presser foot 20 is rigidly secured to the stitching head, and mounted for reciprocatory movements on the head above the foot is a needle 24 which cooperates with a complemental stitch forming mechanism also mounted on said head. A work support d! having a portion located below the foot is pivoted to the standard as at 42 to swing downwardly and forwardly, and is provided with an upstanding guard wall or flange 44 located in front of the standard. The work support carries a work clamp which cooperates with the foot, and means for projecting a ridge of fabric upwardly through the foot into needle penetrating position. The work support is normally held against depression or downward swinging movement by a spring Hi l together with a locking mechanism indicated as a whole by the reference letter X. A trip lever I45 is mounted on the work support for releasing the locking means, and a chain I47 which is connected to the trip lever is adapted to be connected to a treadle or knee-press whereby upon operation of said treadle or knee-press the trip lever I45 will first release the locking means and the work support will then be depressed to facilitate the insertion or removal of the material.

The usual needle thread tensioning means which is indicated at I49, is mounted on the stitching head 8 and includes the usual opposed tensioning plates or discs I50. In order to automatically release the thread tension whenever the work table or support 4| is depressed, I provide a release lever I5i which is pivoted at I52 on the machine frame. The lever includes a crank arm I53 which overlies the flange 44 of the Work support and is equipped with an adjustable abutment screw I5 I for engaging said wall. The lever also includes a release arm I 55 which projects into position for engaging between the tension plates I58. A coil spring I55 encircles the lever and has its end extended for engagement with the frame release arm I55 for holding the abutment screw I54 in engagement with the flange M. Each time the work support is depressed as shown in dotted lines in Figure 4 of the drawings, the release arm I55 will effect a separation of the tension plates I50 and permit the operator to readily withdraw the stitched work from the machine.

It is of course to be understood that the details of structure and arrangement of parts may be variously changed and modified without departing from the spirit and scope of my invention.

I claim:

1. In a blind stitch sewing machine, the combination with a frame, of a horizontal presser foot rigidly secured to said frame, a stitch forming mechanism located above the presser foot and including a reciprocating threaded needle, a work support mounted on the frame to move downwardly and having a portion disposed under the foot, needle thread tensioning means mounted on the frame, and means automatically actuated upon depression of the work support for releasing said thread tensioning means.

2. In a blind stitch sewing machine, the combination with a frame, of a horizontal presser foot rigidly secured to said frame, a stitch forming mechanism located above the presser foot and including a reciprocating threaded needle, 3,

work support mounted on the frame to move downwardly and having a portion disposed under the foot, needle thread tensioning means mounted on the frame and including a pair of spring pressed tensioning discs, and means automatically actuated upon depression of the work support for separating said tensioning discs.

3. In a blind stitch sewing machine, the combination with a frame, of a horizontal presser foot rigidly secured to said frame, a stitch forming mechanism located above the presser foot andincluding a reciprocating threaded needle, a work support pivoted on the frame to swing downwardly and having a portion disposed under the foot, needle thread tensioning means mounted on the frame and including a pair of springpressed tensioning discs, and means automatically actuated upon depression of the work support for releasing said thread tensioning means, said tension release means comprising a release member having a body portion pivotally supported on the frame and crank end portions one of which is disposed in cooperative relation with the work support and the other of which projects between the tension discs.

4. In a blind stitch sewing machine, the combination with a frame including a standard, an arm extending laterally from the upper end thereof, and a stitching head attached to the free end of said arm, of a horizontal presser foot fixed to said stitching head, a reciprocatory threaded needle mounted on the head abovethe foot, a work support pivoted on the standard to swing downwardly and having a portion disposed under the foot, means carried by the work support for projecting a ridge of material upwardly into needle penetrating position, a tensioning means for the needle thread supported on the frame, and means including a lever mounted on the laterally extending frame arm and automatically actuated upon depression of the work support to release said tensioning means.

5. In a blind stitch sewing machine, the combination with a frame including a standard, an arm extending laterally from the upper end thereof, and a stitching head attached to the free end of said arm, of a horizontal presser foot fixed to said stitching head, a reciprocatory threaded needle mounted on the head above the foot, a work support pivoted on the standard to swing downwardly and having a portion disposed under the foot, and also an upwardly extending flange, means carried by the work support for projecting a ridge of material upwardly intoneedle penetrating position, a tensioning means for the needle thread supported on the frame, and means including a lever mounted on the laterally extending frame arm and automatically actuated upon depression of the work support to release said tensioning means, the end of the lever opposite the tensioning means being disposed in front of and engageable by the work support flange when said work support is depressed.

6. In a blind stitch sewing machine, the combination with a frame including a standard, an arm extending laterally from the upper end thereof, and a stitching head attached to the free end of said arm, of a horizontal presser foot fixed to said stitching head, a reciprocatory threaded needle mounted on the head above the foot, a work support pivoted on the standard to swing downwardly and having a portion disposed under the foot, and also an upwardly extending flange, means carried by the work support for projecting a ridge of material upwardly into needle penetrating position, a tensioning means for the needle thread supported on the frame, and means including a lever mounted on the laterally extending frame arm and automatically actuated upon depression of the work support to release said tensioning means, the end of the lever opposite the tensioning means being disposed in front of and engageable by the work support flange when said work support is depressed, and an adjusting screw carried by said end of the lever for engagement with said flange.

7. In a blind stitch sewing machine, the combination with a frame, of a horizontal presser foot rigidly secured to the frame, a stitch forming mechanism located wholly above the foot and including a reciprocatory needle, needle thread tensioning means mounted on the frame, a ridge forming element located below the foot for projecting a ridge of material upwardly through the foot into needle penetrating position, a support for the ridge forming element ,mounted on the frame for movements towards and from the presser foot, means for yieldably urging the support towards the foot, and means automatically actuated upon depression of the support for releasing said needle thread tensioning means.

LOUIS G. BOWMAN. 

